Zephyr AXI GPIO Driver Support

This page gives an overview of the AXI GPIO Zephyr driver which is available as part of the zephyr-amd repo.

HW Features

Support Dual channel
32 max pins per each channel

Design Notes

To run testcase(tests/drivers/gpio/gpio_basic_api/) we need specific loopback design as shown in the following figure,

Vivado block-design excerpt showing the AXI GPIO loopback wiring used by the gpio_basic_api Zephyr testcase: axi_gpio_1 drives gpio_io_o[1:0] / gpio_io_t[1:0] back into a Slice and Concat that loop the bits to gpio_io_i[1:0], with a Constant tying the unused GND input. — AXI GPIO loopback wiring required by the gpio_basic_api test.

Implementation

Zephyr AXI GPIO Driver Implementation

Features Supported

Input/output interrupt support
Input/output polled support
Separate call back configuration for each pin
Support level interrupt

Missing Features

Does not support reading all pin direction in a port
Does not support reading pin configuration (input, output, pull-down, pull-up, active-Low, active-High etc)

Known Issues

N/A

Limitations

N/A

Kernel Configuration

CONFIG_GPIO=y
CONFIG_GPIO_XLNX_AXI=y

Other configuration options:

CONFIG_GPIO_GET_DIRECTION (not supported)
CONFIG_GPIO_GET_CONFIG (not supported)
CONFIG_GPIO_ENABLE_DISABLE_INTERRUPT

Device Tree

AXI GPIO DUAL CHANNEL node

axi_gpio: gpio@81000000 {
        compatible = "xlnx,xps-gpio-1.00.a";
        status = "okay";
        interrupts = <GIC_SPI 90 IRQ_TYPE_LEVEL IRQ_DEFAULT_PRIORITY>;
        reg = <0x81000000 0x1000>;
        gpio-controller;
        #gpio-cells = <2>;
        interrupt-parent = <&gic>;
        xlnx,all-inputs = <0x1>;
        xlnx,all-inputs-2 = <0x0>;
        xlnx,all-outputs = <0x0>;
        xlnx,all-outputs-2 = <0x1>;
        xlnx,dout-default = <0x0>;
        xlnx,dout-default-2 = <0x0>;
        xlnx,gpio-width = <0x20>;
        xlnx,gpio2-width = <0x20>;
        xlnx,is-dual = <0x1>;
        xlnx,tri-default = <0xffffffff>;
        xlnx,tri-default-2 = <0xffffffff>;

        axigpio2: gpio2 {
                compatible = "xlnx,xps-gpio-1.00.a-gpio2";
                status = "okay";
                gpio-controller;
                #gpio-cells = <2>;
        };
};

channel 2 node must be a child node of channel 1 nodes.

AXI GPIO SINGLE CHANNEL node

axi_gpio: gpio@81000000 {
        compatible = "xlnx,xps-gpio-1.00.a";
        status = "okay";
        interrupts = <GIC_SPI 90 IRQ_TYPE_LEVEL IRQ_DEFAULT_PRIORITY>;
        reg = <0x81000000 0x1000>;
        gpio-controller;
        #gpio-cells = <2>;
        interrupt-parent = <&gic>;
        xlnx,all-inputs = <0x1>;
        xlnx,all-outputs = <0x0>;
        xlnx,dout-default = <0x0>;
        xlnx,gpio-width = <0x20>;
        xlnx,is-dual = <0x0>;
        xlnx,tri-default = <0xffffffff>;

};

Driver Stack Size

2.9 KB
- txt - 1.9 KB, data - 1 KB

Example Tests

Test Name	Example Source	Description
AXI GPIO API	tests/drivers/gpio/gpio_basic_api/	functionality check and performs interrupt-based test in loopback configuration

Driver code coverage with gpio_basic_api - 93.8%

Performance Metric

TBA

Mainline Status

Mainlined

Driver Source Path

drivers/gpio/gpio_xlnx_axi.c

Misra C Report

Per coding guidelines of zephyr

Misra-c	driver file	kernel utility	Actual violation
4.6	16	16	0
4.8	2	2	0
4.9	21	21	0
1.2	6	6	0
10.1	24	0	24
10.4	29	0	29
11.5	18	0	18
11.9	1	0	1
12.2	10	2	8
14.4	6	0	6
15.5	6	0	6
15.7	1	0	1
2.5	4	0	4
20.10	2	2	0
21.2	24	24	0
8.13	1	0	1
8.7	8	8	0
Total	179	81	98